/***************************************************************************
 # Copyright (c) 2015-23, NVIDIA CORPORATION. All rights reserved.
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 # modification, are permitted provided that the following conditions
 # are met:
 #  * Redistributions of source code must retain the above copyright
 #    notice, this list of conditions and the following disclaimer.
 #  * Redistributions in binary form must reproduce the above copyright
 #    notice, this list of conditions and the following disclaimer in the
 #    documentation and/or other materials provided with the distribution.
 #  * Neither the name of NVIDIA CORPORATION nor the names of its
 #    contributors may be used to endorse or promote products derived
 #    from this software without specific prior written permission.
 #
 # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS "AS IS" AND ANY
 # EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 # PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 # CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 # PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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 **************************************************************************/
#include "Threading.h"
#include "Core/Error.h"

namespace Falcor
{
namespace
{
struct ThreadingData
{
    bool initialized = false;
    std::vector<std::thread> threads;
    uint32_t current;
} gData; // TODO: REMOVEGLOBAL
} // namespace

static std::mutex sThreadingInitMutex;
static uint32_t sThreadingInitCount = 0;

void Threading::start(uint32_t threadCount)
{
    std::lock_guard<std::mutex> lock(sThreadingInitMutex);
    if (sThreadingInitCount++ == 0)
    {
        gData.threads.resize(threadCount);
        gData.initialized = true;
    }
}

void Threading::shutdown()
{
    std::lock_guard<std::mutex> lock(sThreadingInitMutex);
    uint32_t count = sThreadingInitCount--;
    if (count == 1)
    {
        for (auto& t : gData.threads)
            if (t.joinable())
                t.join();
        gData.initialized = false;
    }
    else if (count == 0)
        FALCOR_THROW("Threading::stop() called more times than Threading::start().");
}

Threading::Task Threading::dispatchTask(const std::function<void(void)>& func)
{
    FALCOR_ASSERT(gData.initialized);

    std::thread& t = gData.threads[gData.current];
    if (t.joinable())
        t.join();
    t = std::thread(func);
    gData.current = (gData.current + 1) % gData.threads.size();

    return Task();
}

void Threading::finish()
{
    for (auto& t : gData.threads)
    {
        if (t.joinable())
            t.join();
    }
}

Threading::Task::Task() {}

bool Threading::Task::isRunning()
{
    FALCOR_UNIMPLEMENTED();
}

void Threading::Task::finish()
{
    FALCOR_UNIMPLEMENTED();
}
} // namespace Falcor
